Headlamp



E. P. BONE.

HEADLAMP.

APPLICATION FILED 1AN.8. 1-920.

Patented Aug. 30, 1921.

lizv'entor EmnBBone Attorney tion at shorter UNITED STATES PATENTOFFICE.

EVAN P. BONE, 0F CINCINNATI, OHIO.

HEAJDIAMP.

To all whom it may concern."

Be it known that I, EVAN P. BONE, a citizen of the United States, and aresident of Cincinnati, in the county of Hamilton and State of Ohio,have invented new'and useful Improvements in Headlamps, of which thefollowing is a full, clear, and eX- act description, reference being hadto the accompanying drawings, forming a part of this specification.

My invention relates to headlamps, and has particular reference to suchheadlamps as are designed for use with motor vehicles.

The principal object of the present invention is to provide in aheadlamp means whereby the projected beam may be defined within limitswhereby glare in the eyes of opposing drivers or pedestrians isprevented.

A further object of the present invention, and one incidental to theprincipal object above mentioned, is to obtain, in connection with theelimination of objectionable glare, improved road illumination.

In order that the roadway may be satisfactorily and economicallyilluminated, it is desirable that substantially even illumination bemade at both long and short ranges. To effect this the rays intended forillumination at long ranges must have greater density than thoseintended for illuminaranges. In headlamps as at present designed andgenerally in use, the beam of light from the lamp fringes away sogradually from the area of greatest concentration of the rays, that ifsubstantially adequate illumination at long ranges be ob tained, therays projected into the eyes of opposing drivers or pedestrians are ofsuflicientdensity to produce undesirable and dangerous glare, even whenthe eyesare not 4 in the portion of the beam of greatest inand to.tensity. This condition results by reason of the fact that the anglebetween the light rays reaching the road at long ranges, which ofcourse, should be the rays of greatest concentration, and those reachingthe eyes of opposing drivers or pedestrians is comparatively small.

In attaining the objects of the present invention, I employ in aheadlamp, an image forming lens having such dimensions that there is aconjugate focal point inside the lamp for each point in the field ofillumination, viz: the roadway and objects upon the side thereof. Theseconjugate Specification of Letters Patent.

Patented Aug. 30, 1921.

Application filed January 8, 1920. Serial No. 350,073.

focal points within the lamp cover an imaginary surface whichapproximates and for all practical-purposes may be spoken of i as aplane. The

illumination, therefore, of any point along the roadway and in thegeneral field of illumination, is dependent jquantity of light emittedfrom view,

along the roadway is effected as desired and,

as will be seen, the illumination of the roadway at long rangesmay beintensified while at the same time the beam is sharply cut off so thatglare in the eyes of approaching persons is prevented.

With the foregoing and further objects in as will more fully hereinafterappear, the present invention consists of details of construction hereinfully described.

In the particular embodiment of my invention selected for illustration-Figure l is a central longitudinal section of a headlamp'constructed inaccordance with this invention.

Fig. 2 is a diagrammatic view, illustratthe principle of operation ofsaid lamp. ig. 3 is a diagrammatic view illustrating the principles ofsatisfactory road illumination.

Fig. 4 is a detail of the screen from the rear.

Fig. 5 is a sectional view of a modified form of screen construction.

The numeral 1 indicates the maincasing or body of the lamp constructedin accordmice with this invention. Mounted in said body is anellipsoidal reflector 2, having. its

foci at 3 and 3 the front portion of the re thereof is approximately inthe cross sec- .generally devoid of spherical aberration.

The use of the aplanatic lens permits the employment of a lens ofextraordinarily wide aperture, in comparison with its focal length,'suchaperture being essential 1n order to accommodate the pencil of rays diverging from the focus at a wide angle, to obviate the necessity ofextreme length in the body of the lamp. The lens as used 1s also anexceptionally wide angle lens but the absence of aberration is notsoessential accordance with optical laws. reflected from the forwardportion. of the except at points near the center of the field.

Mounted in the lamp, in the plane 9-10, is also a screen 6. The screen 6as illustrated in Fig. 4:, is of generally rectangular form and has anupper projection-7 at one side of the middle thereof for the purposehereinafter set forth. The support 8 of the screen 6 is bent so thatthe-vertical section will be removed some distance from the focal plane9-10. As illustrated in Fig. 5, the screen 6 may be arranged forVertical adjustment by means of an electro-magnet 11, operated from aconvenient place in the vehicle. Theforward portion of the support ofthe screen 6 is secured to the body 41 of the lamp by means ofa spring12, which drawsit downwardly against the threaded pin 13. The support ofthe screen. 6 is pivoted at 14, and as will be seen when theelectro-magnet 11' is energized the screen will be raised against thetension of the spring 12.

The lamp is provided with a socket for an electric bulb 15, the filamentof which is located at the focal point3" of the reflector 2. Thereflector incloses the bulb so as to collect a major portion of the raysradiating therefrom.

The principle of operation 'of the device is illustrated in the severalfigures of the drawings by means of typical rays indicated by brokenlines. Rays from the filament of the bulb 15 striking the ellipsoidalportion of the reflector 2 are concentrated in the plane 9-10, aroundthe point 3, the crosssectional area of the concentration beingproportional to the size of the filament, in Other rays reflector passthe. focal plane 9-10 at vari ous points, the density thereof decreasinggradually away from the area of concentration at 3. The forward portion,of the reflector extends well into the front half of the lamp, causingrays to enter the lens from exceptionally wide side angles to make"possible the illumination of a correspondingly wide field. The lens 5is, as above stated, arranged relative to the plane 910, so that saidlens throws an optical image .of whatever may be located in said planeinto the field of illumination'and the mapping out of the lightdistribution over the plane forms a plan, in miniature, of the lighttration 3, in the plane 910, being of maxi:

'mum density, the projected image thereof will be more brightlyilluminated, and this portion of the optical image is indicated at 17.All of the rays passing the plane 9--10 at any other one pointas forinstance 18, in Fig. 2, will be projected to its conjugate focal pointin the optical image, for instance the point 19 on the plane 16. Therays at the point 18, however, being of less density,

as above set forth than the rays at the point 8 in the area ofconcentration, said portion of the image will be of correspondingly lessbrilliance, as indicated in the image on the plane 16; and as aforesaid,as the density 'graduallydecreases to the edges from the point 3, thebrilliance of the image gradually decreases radially from the area ofgreatest brilliance 17. The screen ,is located in the focal plane 9--10of the lens 5, and the image of, said screen will therefore be projectedwith sharp definition into the field of illumination. as indicated at 20on the plane 16, the downwardly projecting portion 21 to the left of thecenterof illumination 17 as viewed from the lamp,being the optical imageof the upper projection 7 of the screen 6.

The screen is opaque and therefore blocks out rays from the portion ofthe focal plane covered by it; hence the portions 2021 of the field ofillumination are in. comparative darkness. It is, of course, only'byplacing the screen 6 in the focal plane of the-lens 5 that sharpness ofdefinition of the area of area may be located at theproper angle ofSince however, the

elevation above the roadway at practlcable operating ranges, this anglebeing very small. Thus the screen forms a partial border to theconcentrated area around 3, so that,

the dark area 20-21 in the image appears to partly border the brightarea 17 The dark area must, however, only partly border the bright areaso as not to cut off the light below 17 which is needed for close, rangeillumination.

From the foregoing description of the optical principle of the lamp itmay be noted that two distinct means,the reflector and the screen,areused for controlling the intensity of the light emitting from thevarious points in the plane 9-10 to the lens.

The reflector operates with economy while the screen operates withprecision and each is used where its particular feature is most needed.The reflector is economical because it functions without loss of lightby interception as the rays pass the plane; and having any fixedavailable quantity of light radiating from the filament source, the sameis collected by the reflector which by the varying angles of its surfacedirects said light to the various points in the plane with aconcentration and distribution best suited for illumination. However, byreason of the appreciable size of the source of light, infperfections inthe reflector, and deviations of the source of light from accuratelocation in the focus of the reflector, the concentration of the rays atany particular point as intended is indefinite, causing a blurringeffeet. This effect is not necessarily obj ectionable except at certaincritical locations where bright light as emitting from certain pointsmust be prevented from closely adjacent points. Atsuch locations thescreen is used and, although losing light by interception, it serves toblock out the rays alongsharply defined limits with the accuracyrequired to illuminate the roadway at long range without projectingglaring light into the eyes.

Changesmay be made from the precise formof headlamp herein shown anddescribed, within the scope of accompanying claims, without departingfrom the principles of my invention and Without sacrificing its objectsand advantages. a

In order to utilize some of the intercepted light the screen 6 may havea reflecting sursold reflector 2.

face, 6 In Fig. 5 of the drawings 1 have illustrated the intercepted ra'2!) being reflected as shown by the line 30 to the ellip- In Fig. 3' Ihave illustrated diagrammatically the application of the present lamp toroad conditions. In said figure the arc 22'23 represents the angle ofthe projected beam of sufficient intensity for useful illumination, andwhile this beam is of greatest intensity near the center, except wheredarkened by the screen, it is at all points within this angle of suchbrillianey as to cause objectionable glare. In placing the lamp 24 onthe vehicle, the same is so disposed with relation thereto that thebright central portion 17 of the optical image reaches the roadway at 25and the area of darkness 20, the

central portion 25 of the beam, the density of the rays reaching theroadway decreases from the central portion toward the vehicle. As theshorter distances require less flux density than the greater ranges toobtain equivalent illumination, this decreasing of the density from thecenter serves to give the roadway a nearer uniform illumination. Thedistribution of-the lightalong the roadway in this manner accords withthe stand ards of efliciency'and economy in headlighting for the reasonthat the illumination at close ranges does not have to be unduly brightinorder to obtain sufiicient brightness for long range. The angularwidth of the close range illumination is of necessity greater than thatof long ranges. The distribution of light as illustrated on planesurface 16, shows how the concentrated area 17 .is only a smallpercentage of the total area light at .27, within the necessarily smallangle.

The dark area 21, produced by the projection 7 of the screen 6, is onthe left side of the roadway as viewed'from behind the lamp and comesinalinement with the position of an approaching vehicle when the twovehicles have turned aside to pass, thus providing an additional factorof safety against glare when the car having these headlamps receivesupward tilts from uneven roads or abnormal loading. The screen formingthe dark area 2021 may in various shapes and sizes as is consistent withthe general object of preventing glare and providinglongrange-illumination during the greatest number of circumstances on.varied road conditions. -Inasmuch asthe positions of theeyes ofopposing drivers are, in general, above and to the left of the surfaceof the roadway, the darkened area is correspondingly disposed, ingeneral, above and to the left of the central portion of the beam.Whether it isentirely above, entirely tothe side, or both, and ofwhatever size'andproportions is a matter of design or specifiedrequirements. It will be understood that the geometrical-relations ofthe size and shape of the dark areal20-21 to" the illuminated areas 17,"etc., are similar'to those of the however, be designed p screen 67 tothe concentrated light in the plane 9-10 in accordance with well knownlaws of optics.

The means provided in this invention for projecting areal optical imagedo not necessarily have to be of a structure permitting the degree ofrefinement required in devices generally used for projecting imagesupona screen to form pictures.

By means of the; adjusting mechanism points inside the body of said lampconju=, w gate with a field of desired illumination,

means for concentrating rays from said source of light at a point'in thefocus of said lens inside the lamp, and means for distributing rays fromsaid source .in gradually decreasing density radially from said point ofconcentration over 1 the focal plane of said lens inside the lamp.

2. In a headlamp in combination with they casing and a source of light,a. projecting lens mounted 1n sa1d casing, having focal points insidethe body of said lamp conjugate with a field of desired illumination, anellipsoid reflector for concentrating rays from said source of light ata point in the focus of said lens inside the lamp, and a reflector fordistributing rays from said source in gradually decreasing densityradially from said point of concentration over the. focal plane of saidlens inside the lamp.

3. In a headlamp in combination with the casing and a source of light, aprojectin lens mounted in said casing, havlng focal points inside thebody of said lamp con ugate with a field of desired illumination,

means for concentrating rays from said source of light at a point in thefocus of said lens inside-the amp, means for,d1s-

tributing rays from said source in gradu-' ally decreasing densityradially from said point of concentration over the focal *plane of saidlens inside the lamp, and means for intercepting a portion of said rays.1 Y

- 4. In a headlamp in combination with the casing and a source of light,a projecting lens mounted in said casing, having focal points inside-the body 'of said lamp conjugate ,with a field of desired illumination,an ellipsoid reflector for concentrating rays from said source of lightat a point in the focus of said lens inside the lamp, a reflector thefocal plane of said lens for interceptmeans for concentrating raysfromsaid for distributing rays from said source in gradually decreasingdensity radially from said point of concentration over the focal planeof said lens inside "the lamp, and means for interceptinga portion ofsaid rays. i 5. Ina headlamp in combination withthe casing and a sourceoflight, a projecting lens mounted in said casing, having foca pointsinside the b0dy of said lamp conjugate with a field of desiredillumination,

means for concentrating rays from. said source of light at a point inthe focus of said lens inside the lamp, means located in ing a portionof said rays, and means for moving said intercepting means in saidplane.

6 In a headlamp in combination with the casing and a source of light, aprojecting lens mounted in said casing, having focal points inside thebody of said lamp conjugate with a field of desired illumination,

source of light at a point in the focus of said lens inside the lamp,means for distributing rays from said source in: gradually decreasingdensity radially from said point of concentration over the focal planeof said lens insidethe lamp, means for intercepting a portion of saidrays, and means for moving said intercepting means in said plane. r

7 In a headlamp in combination with the casing and a source of light, aprojectin lens mounted in said casing, having foca points inside thebody of said lamp conjugate with a field of desired illumination, anellipsoid reflector for concentrating rays from said source of light ata point in the focus of ssaid lens inside the lamp, means forintercepting aportion of said rays, and means'for moving saidintercepting means in said plane. 1

8.' In a headlamp in combination with the casing and'a, source of light,a project-' ing lens mounted in said casing, having focal points insidethe body of said lamp conjugate witha field of desired illumination, anellipsoid reflector for. concentrating rays from said source of lightata oint in the focusiof said lens inside "the amp, a reflector fordistributing rays from said source in graduallydecreasing densityradially from said ointof concentration over the focal planeof s'aidlensinside the lamp, means for intercepting a portion of said rays, andmeans for moving said intercepting means in. said plane.

9. In a headlamp in combination with the casing and a source of light,anaplanatic projecting lens mounted in said casing, havmg, focal pointsinside the 'body of said. lamp conjugate witha field of desiredillumination, means fofponcentrating rays from said source of light ata-point in the focus of said lens inside the lamp, means located in thefocal plane of said lens for inter cepting a portion of said rays, andmeans for moving said interceptingmeans in said plane.

10. A headlamp comprising an ellipsoidal reflector, a source of light atone focus of the reflector, an aplanatic lens in the'lamp having aprincipal focus at the other focus of the reflector, and lightinterceptingjmeans mounted within the lamp laterally adjacent saidprincipal focus of the lens.

11. In a headlamp of the character, indi cated, the combination of anelectric incandescent source oflight, a lens having its rearwardfocal'plane within-the headlamp; and a deeply cupped ellipsoidalreflector to direct a preponderanceof the light rays toward said lens,said reflector having one focus at said. source of light and the othersubstantially at said rearward'focal plane of the lens, and a screensubstantially in said focal plane and encroachlng upon the of the lens,and having said adjacent re area of intense light concentration atoneside thereof; i

12. In a headla of the character indicated, the combination of anelectric incandescent source of light, a lens having its rearward focalplane within the headlamp,

and a reflector surrounding the source of light hemispherically andextended thence forwardly to direct a preponderance ofthe light ra 5toward said lens; "said reflectorbeingformed with its closed endellipsoidal and "having one focus at the source of llght and the otherat the rearward focal plane fleeting surfaces of lesser curvature,whereby the distribution of light-rays .insaid rearward focal planecomprises a compare.

tively small-area of. intense concentration surrounded-by ,a large areaof lessconcentration; and-a screen so placed as to partly encroachtration.

uponsaid area of intense concen .trated, said I13. In alight'concentrating and projecting device, the combination of a. sourceof llght; means for concentrating the rays of 1 said light within thedevice, means for proectmg the ra s of sand light when concenatter meanshaving a' focal plane within the device, the concentrating focal planewithin the'headlaiv p, a light' concentrating reflector adapted toproduce its area of greatest light concentration in. the rearward focalplane of said lens and a screen substantially in said focal plane andpartly encroaching upon said area of great est-light concentration butnot surrounding same.

15. In a headlamp havinga source of light; a reflector having anellipsoidal surface to produce the greatest light concentration withinthe lamp; adjacent portions of said reflector having a lesser curvaturethan said first mentioned ellipsoidal portion, a

lens in the front of said lamp whose rearward principal focus issubstantially in the same cross-sectional plane as said greatest lightconcentration and a screen substantially in said plane of the focus andlight concentration area so placed as to partly encroach upon said areaof greatest light concentration but not surround the; same.

16. In combination with a headlamp having a sourceof'light,'a lightconcentrating reflector and a lens having its rearward principal focuswithin the headlamp; 'a screen stantiall y in the rearward focal planeof said .lens and contiguous to said focus and only partly surroundinsaid focus. A E P. BONE

